Heretofore, a heat exchange plate for use in heat exchangers and the like is desired to have a high heat conductivity. For improving the heat conductivity, it is better to form micron-order fine irregularities on the surface of the plate. As a method for transferring such micron-order fine irregularities, a number of techniques have been developed, for example, as shown in Patent Document 1.
According to the transferring method onto the surface of a metal plate in Patent Document 1, a metal sheet is carried by the rotation of carrying rolls. Further, by pressing the irregularities-formed transferring part of the outer periphery of a transfer roll against the metal sheet being carried, a transferred part of irregularities that are almost the same as those of the transferring part of the transfer roll is formed on the surface of the metal sheet.